The present invention relates to structural panels and more particularly concerns such panels and methods for their manufacture that employ filler materials and reinforcing structures arranged to provide a unitary panel structure.
Light-weight plastic materials, including the many different types of foamed synthetic resins and expanded foams, such as urethanes, polystyrenes and the like, have a number of properties that are highly desired in building materials for various types of structures such as walls, roofs and the like. These properties include light-weight, exceedingly low thermal conductivity, resistance to abrasion, impermeability to moisture, and acoustic insulation. However, such materials generally have insufficient structural strength for some applications and, therefore, must be combined in some manner with other materials having satisfactory structural properties.
Various configurations employing combinations of light-weight cellular plastic foam or expanded plastic bodies and rigid load-bearing structural elements have been suggested in the past for providing structural building panels that can effectively utilize the desirable properties of the cellular materials. Typical of such prior arrangements are the U.S. patents to Weismann U.S. Pat. Nos. 3,305,991, 3,555,131 and 3,879,908. In the first two of these patents, a three-dimensional wire matrix is first manufactured and thereafter a light-weight plastic core is provided by pouring a liquid foaming plastic which foams in place within the framework. However, because the cellular material is foamed in place, a form must be provided to define the bottom surface of the foam core. Difficulties have been encountered in maintaining the form in a planar configuration and in positioning the form at a precise distance from the outer surface of the framework. Further, since no form is generally employed to define the surface of the foamed-in-place core (the panel core is foamed in place within the structural framework, with the panel in a horizontal position according to the teachings of the patents), the core will exhibit an outer surface that is far from the desired planar condition. It will exhibit a surface of such irregularity and imprecise location that the foamed core may actually contact the outer elements of the structural framework in many places thereby preventing a subsequent coating from completely encompassing such outer portions of the framework.
The later patent to Weismann, U.S. Pat. No. 3,879,908, avoids some problems of the use of foamed-in-place material. After building a completed three-dimensional wire framework, the patentee here inserts a plurality of insulative elements through passages that are formed and disposed wholly within the structural framework. These insulative elements must be dimensioned so as to freely and easily pass between adjacent elements of the structural framework and when positioned will not have adjacent surfaces in contact with one another. Thus, impermeability to moisture, sound and heat is significantly degraded. Moreover, the relatively free insulative elements add little to the strength of the completed composite panel. After such insertion, a bonding agent is employed in the arrangement of the U.S. Pat. No. 3,879,908 to secure the insulative elements in position within the lattice so that the final coatings may be applied to the panel surfaces after the panel has been erected in the field.
In my co-pending application for Structural Panel, Ser. No. 857,235, filed Dec. 5, 1977, there is described a composite structural panel and method for its manufacture that eliminates or avoids many of the above-mentioned problems. In the arrangement of my co-pending application, a number of pre-formed, long, narrow filler elements are stacked in consecutive alternation with flat trusses to form a panel subassembly that is thereafter compressed to embed the strut members of the wire lattice into the faces of the mutually contacting foam filler elements. While in such compressed condition, cross members are welded to the truss runners to hold the panel in assembled condition with the filler elements positioned substantially symmetrically of the panel and spaced equally from opposite surfaces of the panel.
The panels constructed according to my co-pending application have been successfully, efficiently and economically employed in the construction of a number of houses. After erection at the building site, these panels have a coating of concrete or plaster applied to entirely cover both panel surfaces, completely embedding the protruding wire structure therein and thus forming the exterior surface of the completed panel.
For a panel of a thickness of three inches before the application of the finished coating (which is the thickness of panels presently constructed according to the teachings of the co-pending application) and foam elements of two to two-and-one-half inch square cross section, a concrete or plaster coating of approximately seven-eights to one inch is applied to each side for panel finishing.
It is found that for many applications a total thickness of concrete of nearly two inches is not required either for panel strength or protection or to meet any code or Governmental regulations. Further, in the erection of such panels, they are commonly braced by means of diagonal braces extending out from the panel on each side, both inside and outside. These braces form obstacles encountered by the workmen in moving concrete application hoses about for the application of coatings.
Where the panel is to be used as a roof panel, the interior coating of the panel must be applied to a horizontal or somewhat inclined surface that may form a ceiling of the completed structure. To apply a coating to such a downwardly facing surface in a thickness of nearly one inch is difficult or impossible to achieve in a single application with many coating materials.
In use of composite structural panels, primary considerations are cost, both of materials and labor, and cost of erection and installation. Thus, for those walls such as interior walls which may require less structural strength, coatings other than concrete are desirably employed and walls with hollow cores are preferable because of the decreased cost of materials. Hollow core elements such as the paper tubes described in Weismann U.S. Pat. No. 3,879,908, provide some of the advantages of the hollow core but do entail considerably increased expense because of the significantly greater cost of fabrication of such hollow core elements.
Accordingly, it is an object of the present invention to avoid or eliminate above-mentioned problems and to provide a structural panel of high strength and low cost that permits rapid, efficient erection and coating in the field, the panel having the desired structural, moisture, acoustic, thermal and other desired characteristics.